Sulfur-containing polymeric compounds



Patented Apr. 15, 1947 uNi'rE STATES PATENT OFFICE 1 SULFUR- CONTAININ GPOLYMERIC COMPOUNDS Emmette F. Izard, Kenmore, N. Y., assignor to E. I.du Pont ale Nemours & Company, Wilmington, Del., a corporation ofDelaware No Drawing.

7 Claims.

The invention Application January 19, 1944, Serial No. 518,877

units, which units may be cyclic or acyclic in nature, and which arelinked together within the compound in chain-like fashion. The compoundmay be a naturally occurring one or may be partly or wholly synthetic.Cellulose is an example of a naturally occurring polymeric material,while examples of partly or wholly synthetic polymeric mers, includingsuch substances as the polyesters and polyamides of polycarboxylicacids,synthetic resins and the like. Generally, Polymeric materials of thetype intended for use with this invention possess an average molecularweight in excess of 1000, and exist in the free state as solids at roointemperature and atmospheric pressure.

It is an object of this invention to provide a new and useful polymericmaterial containing sulfur. Another object of this invention is toprovide a polymeric material having sulfur-containing functional groups.A still further object is to provide a process of preparing theaforementioned polymeric materials, which process is easy ofaccomplishment and readily controlled. Other objects of the inventionwill appear hereinafter.

The objects of this invention are accomplished by reacting a thiosulfatetaken from the class consistingof alkali metal, ammonia and aminethiosulfates with a reactive group of a polymeric .material to form onsaid polymeric material a thiosulfate functional group and reacting twoof the said thiosulfate functional groups of the polymeric material toform a cross-linked polymeric material. The'latter reaction will takeplace in the presence of heat or a mild oxidizing agent. Thecross-linked polymeric material exhibits a materially lower solubilityin water or commonorganic solvents than the original polymer or itsthiosuliate derivative.

A further object of this invention is accomplished by reacting thecross-linked polymeric material with thioglycolic acid to produce amercaptan.

The present invention will be more clearly understood by reference tothe following detailed examples, it being understood, however, thatthese examples are illustrative and that the scope of the invention isnot to be limited thereto. Throughout the examples, the parts ofsubstances referred to are parts by weight unless otherwise indicated.

Example] A solution oi 160 parts of polyvinyl chloracetate (prepared bythe polymerization of vinyl chloracetate in the presence of peroxide) in640 parts of methyl Cellosolve (mono methyl ether of ethylene glycol)was treated at a temperature of 80 C., with a solution of 310 parts ofhydrated sodium thiosulfate in 310 parts of water. The sodiumthiosulfate reacted with the polyvinyl chloracetate and the mixturebecame homogeneous within 5 minutes, after which it was immediatelycooled to room temperature. It gave a negative test for sodiumthiosuliate. The product was soluble in water and in methyl Cellosolve.It was coagulated by a 50-50 mixture of alcohol and acetone, andanalysis indicated that approximately 92% of the chlorine atoms-of'thechloroacetate groups had been replaced by sodium thiosulfate groups.

A methyl Cellosolve solution of the above-mentioned product was castonto a heated plate to form a thin, transparent film. The dried film,which was still water-soluble, was then treated for 1 minute with asolution composed of 98 parts of alcohol and 2 parts of iodine,whereupon it became insoluble in and insensitive to water and commonorganic solvents, including methyl Cellosolve. Sulfur analysis agreedwith the theoretical value for a compound of the structure,

' caused the film to again become water-soluble.

The amount (1.525 parts) of thioglycolic acid per part of polyvinylchloracetate originally used to produce the insoluble film was requiredfor complete reaction. Preferably, the thioglycolic' vinylthioglycolate.

Example If A p-toluene sulfonate derivative of cellulose acetate wasprepared in the following manner. 400 parts of dry cellulose acetatecontaining 1.66 acetyl groups per glucose unit were dissolved in 1475parts of pyridine and treated with 400 parts of p-toluene sulfonylchloride dissolved in 295 parts of pyridine, the mixture being cooledwith water until the initial evolution of heat had subsided, after whichit was allowed to stand for 4 hours at room temperature and was finallycoagulated in water.

wherein the symbols Ac represent acetyl groups and the glucose units areportions of the 450 parts of the resulting p-toluene sulfonatederivative of cellulose acetate (containing.l.66 acetyl groups and 0.29p-toluene sulfonate groups per glucose unit) were then dissolved in amixture of 792 parts of acetone, 966 parts of methyl Cellosolve and 100parts of water. The solution was heated to 63 C., and a mixture of 250parts of sodium thiosulfate pentahydrate, 97 parts of methyl Cellosolve,and 125 parts of water were added. At the end of 2 /2 hour s .themixture was cooled to room temperature and=water was slowly added untilthe polymeric-. material coagulated. The coagulated material- -thusobtained was washed and dried at 65C.- 440 parts of a product containing4.28% of sulfur (corresponding to 0.075 thiosulfate groups and 0.215p-toluene' sulfonate' groups per glucose unit) were obtained. Thematerial resembled cellulose acetate in its solubility characteristicsand, like cellulose acetate, the material was soluble in a mixture of 50parts of acetone, 10 parts of water, and 40 parts of methyl Cellosolve.A solution of the material in such a mixture was suitable for thecasting of films or for. the spinni-ng of yarns by the dry spinningprocess. Typical yarns obtained in this manner possessed a tenacity of 1gram per denier and {an elongation of 36%.

' Samples-of cast film/when heated in air at 100 C., for a p'eriod'of.minutes, were rendered substantially completelyinsensitive to water andinsoluble in common organic solvents or mixtures H H -o-c c-o- Ri -0A0Ari-042E Ac-O H o o HC-OAc H --n .11 an at s-s on v n n same or adjacentpolymeric molecules. When subsequently treated with an acetone solutionof thioglycolic acid in the manner of Example I above, the films becamesoluble in organic solvents and showed a positive test for the presenceof thiol groups.

Example I H insoluble in water, but readily soluble in a mix-' ture ofalcohol and water. The dry product contained about $4 mol acetalsubstitution per polyvinyl unit.

parts of the polyvinyl chloracetal were dissolved in a mixture of 250parts of methoxy ethanol and 350 parts of water. 50 parts of hydratedsodium thiosulfate in parts of water were added to the solution and themixture heated on a hot water bath with stirring for 3 hours, at whichtime a homogeneous smooth solution had been obtained. To complete thereaction, the solution was heated for an additional 10 hours at 90 C. Afilm of this solution was cast on glass, dried at 65 C. and washed withwater. The film was then treated with hydrogen peroxide, whereupon itbecame insoluble in and insensitive to water and common organicsolvents. Analysis of this insolubilized film, after washing and drying,indicated the absence of chlorine and the presence of a substantialamount of sulfur, and its properties indicated it to be cross-linked.

The above detailed examples illustrate embodiments of the presentinvention wherein a thiosulfate is reacted with three specific polymericmaterials containing specific reactive groups, namely, a polyvinylcompound containing a chloracetate reactive group (Example I), celluloseacetate containing a p-toluene sulfonate reactive gro' .13 (Ex-- ampleII), and a polyvinyl compound containing a chloracetal reactive group(Example 111) The present invention is not, however, to hem limited. Inits broad scope, the present invention relates to the treatment withathiosulfate, of any polymeric material containing any reactive groupwhich will react with the thiosulfate to form on said polymeric materiala, thiosulfate-containing functional group.

As examples of other polymeric materials which may contain functionalgroups which are reactive with a thiosulfate to produce a polymericmaterial having thiosulfate-containing functional groups, the followingmay be named: vinyl polymers, polyacrylic compounds, polymeric resins,cellulose derivatives, linear condensation polymers, for example,synthetic resins, synthetic linear condensation polyamides, polyesters,polyethers and polyanhydrides, and the like, provided only that thepolymeric material contains, or can be made to contain, a reactive orfunctional group which is reactive with the thiosulfate to produce apolymeric material having a thiosul- "fate-containing functional group.

As examples of reactive groups, which may be contained in the polymericmaterial to react with the thiosulphate in accordance with theinvention,

ducted in the presence of an inert solvent with which only one of thereactants is miscible. The use of such a solvent, of course, generallyrequires somewhat longer, more rigorous treating conditions. Under thepreferred conditions, as indicated above, it is usually sufficient toheat the polymeric material with the thiosulfate on a water bath forperiods of from 1 to 24 hours. The extent of the reaction variesdirectly with the rigorousness oi. the reaction conditions.

Because of their ready availability and relative stability, it ispreferred to employ an alkali metal thiosulfate in the practice of thisinvention, and of these sodium thiosulfate is preferred. ,However, thisis not essential, and other alkaline thiosulfates, including ammoniumthiosulfate, magnesium thiosulfate, and amine thiosulfates, can beemployed if desired.

As above stated, this invention also contemplates the cross-linking ofthe polymeric materials having the thiosulfate-containing functionalgroups as obtained by the reaction with the thiosulfate. Suchcross-linking of the polymeric materials is of particular value where itis desired to make the original polymeric material or their sulfurcontaining derivatives less soluble in water or common organic solvents.As shown in the examples, this cross-linking and insolubilizing of thepolymeric thiosulfate derivatives of this invention are brought about bysubjecting the thiosulfate derivatives to oxidizing conditions, i. e.,heating these derivatives aloneor in the presence of air or by treatingthem with mild oxidizing agents, such as iodine, peroxides,ferricyanides, dilute nitric acid, and the like. Such heating or mildoxidation destroys the thiosulfate portion of the thiosulfate-containingfunctional groups of the polymeric material, and causes the residualportions of adjacent pairs of such groups to combine to form an -SS--(disulfide) link. These pairs may be members of the same or adjacentmolecules of the poly-' meric material.

The degree of insolubility of the final crosslinked polymeric materialobtained varies directly, of course, with the number of thiosulfategroups inserted by the reaction of this invention in the polymericmaterial andv destroyed by the heating or oxidation treatment, and isalso somewhat afiected by the solubility characteristics of the originalunreacted polymeric material. For example, in the case of the polyvinylchloracetate employed in Example I, the thiosulfate derivative obtainedwhen only of the available chlorine atoms have been replaced bythiosulfate can be rendered water-insoluble by ox d tion with alcoholiciodine, although it will still be somewhat swollen bywater' and thecommon organic solvents. This degree of watersensitivity and organicsolvent-sensitivity is rapidly reduced, however, as the degree ofsubstitution is increased, and it has been found possible by means ofthis invention to replace up to and including 100% of the chlorine atomswith thiosulfate groups, thus making possible the production of acompound that possesses the maxi mum number of -SS groups, whichcompound is marked by its complete insolubility in and insensitivitytoward water and common organic solvents.

As shown in the examples, the process of this invention makes possiblethe preparation of water-insoluble and organic solvent-insoluble shapedarticles of polymeric materials. A shaped article is preferably preparedfrom the soluble thiosulfate derivative of the polymer obtained inaccordance with the present invention. However, this is not essentialand the entire treat ment, including modification of the polymer toinsert a reactive groupand subsequent treatmentwith sodium thiosulfateand then with an oxidizing agent, can, if desired, be conducted on apre-formed polymeric article. Thus, for example, a formed structure,such as a sheet of regenerated cellulose, can be surface-esterified withp-toluene sulfonyl chloride, the. resulting ester then being treated insheet form with sodium thiosulfate and subsequently oxidized to form awater-insoluble and organic solventinsoluble sheet.

This invention provides a simple and easily controlled process for theintroduction of sulfur into a polymeric material, the sulfur beingpresent as a thiosulfate functional group. When such athiosulfate-containing polymeric material issubsequently heated ortreated with a mild oxidizing agent, a sulfur cross-linkage is createdbetween adjacent chains of the polymer. The presence of such linkagesrenders a polymeric material less soluble in and less sensitive to waterand common organic solvents and the invention thus provides a simple,easilycontrolled process for the insolubilization of a polymeric.material. In certain instances (when the thiosulfate. derivative of thepolymeric material is insolubilized by being subjected to oxidizingconditions such as heat or treatment with a mild oxidizing agent), theinsoluble product obtained can be restored to a soluble state, and againrendered insoluble by heating or by treatment with an oxidizing agent.The process of the invention lends itself to the treatment of pre-formedarticles of a polymeric material. The process does not give rise to theformation of undesirable by-products, the polymeric material finallyobtained being substan-. tially free of such compounds and possessing alight color. Because of the presence of the sulfur in the final product,yarns produced in accordance with the invention resemble wool in many oftheir characteristics.

Since it is obvious that many changes and modifications can be made inthe above-described details without departing from the'nature and spiritof the invention, it is to be understood that the invention is not to belimited to the details described herein except as set forth in theappended claims.

I claim:

1. A saturated macromolecular organic com-- pound havingat least onerecurringunit linked together in chain-like fashion inthe molecule tothe chain of the macromolecular compound and to a second oxygen atom byonly one bond,

and (c) a carbon atom which. in turn, is attached to both an oxygen atomdirectly attached to the chain of the macromolecular compound and to asecond'oxygen atom by two bonds, the second valence of the sulfur atombeing satisfied by a memberof thel'grcup consisting of hydrogen andanother bivalent sulfur atom whose second valence is satisfied in thesame manner as i the first valence of the first-named sulfur atom.

2. A saturated macromolecular organic compound having at least onerecurring unit linked together in chain-like fashion in the moleculethereof, an average molecular weight in excess of 1000' and containingsulfur and wherein the first valence of a bivalent sulfur atom isattached through a methylene group to a carbon atom which is in turnattached to both an oxygen atom attached directly to the polymer chain,the second valence of the sulfur atom being satisfied by a member of thegroup consisting of hydrogen and another bivalent sulfur atom whosesecond valence is satisfied in the same manner as the first valence ofthe first-named sulfur atom.

3. A saturated macromolecular organic compound having at least onerecurring unit linked together in chain-like fashion in the moleculethereof, an average molecular weight in excess of 1000 and containingsulfur and wherein the first valence of a bivalent sulfur atom isattached through a methylene group to a carbon atom which is in turnattached to both an oxygen atom attached directly to the polymer chainand to another oxygen atomby at least one bond, the second valence ofthe sulfur atom being satisfied by a member of the group consisting ofhydrogen and another bivalent sulfur atom whose second valence issatisfied in the same manner as the first valence of the first-namedsulfur atom.

4. A saturated macromolecular organic compound having at least onerecurring unit linked together in chain-like fashion in the moleculethereof, an average molecular weight'in excess of 1000 and containingsulfur and wherein the first valence of a bivalent sulfur atom isattached through a methylene group to a carbon atom which is in .turnattached through an oxygen 8 atom directly to the polymer chain and toone other oxygen atom by two bonds, the second" valence of the sulfuratom being satisfied b! a member of the group consisting of hydrogen andanother bivalent sulfur atom whose second valence is satisfied in thesame manner as the first valence of the first-named sulfur atom.

5. A cross-linked saturated macromolecular organic compound having anaverage molecular weight in excess of 1000 and containing within itsstructure units corresponding to the formula on, on,

6. Polyvinyl thioglycolate.

7. A cross-linked saturated macromolecular organic compound having anaverage molecular weight in excess of 1000 and containing within itsstructure units corresponding to the formula wherein the symbols "Ac"represent acetyl groups, and the glucose units are portlons'of polymericmolecules.

EMME'I'I'E F. IZARD.

REFERENCES CITED.

The following references are of record in the file of this patent:

UNITED STATES PATENTS

